1. Field of the Invention
This invention relates to antiperspirant emulsions and more particularly to stable antiperspirant emulsions containing major portions of volatile cyclic silicone, water, and antiperspirant salts.
2. Description of the Prior Art
Antiperspirant compositions adapted for roll-on application which have achieved substantial consumer acceptance include such compositions as are described, for example, in British patent application No. GB 2018590 A. Such compositions are substantially anhydrous and comprise a powdered antiperspirant agent suspended in a liquid hydrophobic volatile silicone vehicle (generally 60 to 95% by weight) which includes a hydrophobic suspending agent, the composition containing less than 4% of other hydrophobic liquids which are less volatile than the cyclic silicone. These compositions have excellent "feel," are neither sticky nor tacky, apply smoothly, and dry quickly.
Having achieved these desirable properties, it would nevertheless be avantageous to the formulator to reduce the cost of the composition described above by replacing the expensive volatile cyclic silicone, or at least a major portion thereof, with water, while at the same time avoiding a sacrifice of the above-mentioned desired properties. This goal might be achieved by retaining some of the silicone, for the quick drying and good "feel" it affords to the product, while providing a stable emulsion with a major portion of water, in the presence of the antiperspirant ingredient.
Such an approach has been proposed, for example, in a publication of the Product Development Department of ICI Americas Inc., entitled "Antiperspirants: Functionality and Benefits of ICI Americas' Surfactants and Emollients" (1980), wherein at page 32 it is proposed to emulsify a quick-drying aluminum chlorhydroxide antiperspirant lotion including volatile cyclic silicone and water with a surfactant mixture of polyethylene glycol (2) cetyl ether and polyethylene glycol (23) lauryl ether, which surfactants are present in a ratio of 3.4:1 and together account for 4% by weight of the total composition. Although the volatile silicone requires HLB 8 and the surfactant mixture described can be shown to have HLB32 7.9, the emulsion is not stable. Further attempts to create a stable antiperspirant emulsion of volatile cyclic silicone and water, using a surfactant mixture at HLB 8 of polyethylene glycol (20) stearyl ether or polyethylene glycol (20) cetyl ether, together with polyethylene glycol (2) stearyl ether, also were not successful.